80 Chapter 3
the outbreaks. These included storage of raw
milk at elevated temperature, which enabled
bacterial growth, no use of starter culture,
and a less than adequate maturation time.
Within Europe, non - 0157 : H7 VTEC
infections are considered equally as impor-
tant as 0157 : H7. Germany (Gerber et al.,
2002 ), Italy (Tozzi et al., 2003 ), and Denmark
(Pierard et al., 1999 ) reported that more than
40% of confi rmed cases of VTEC - related
HUS were caused by non - 0157 : H7 VTEC.
In 2005, French raw milk Camembert - type
cheeses contaminated with E. coli 026 and
080 caused 16 HUS cases and a national and
international recall of the entire production
of cheeses (Espie et al., 2008 ).
Different cheese varieties have had evi-
dence of VTEC contamination, based on the
presence of shiga toxin (stx) or isolated
VTEC (Pradel et al., 2000 ; Fach et al., 2001 ;
Hussein and Sakuma, 2005 ; Vernozy - Rozand
et al., 2005 ; Rey et al., 2006 ; Caro and
Garcia - Armesto, 2007 ; Stephen et al., 2008 ).
Irrespective of the detection methods used,
published studies report the incidence of
VTEC 0157 : H7 and other serotypes in both
hard and soft cheeses as consistently low.
Furthermore, many reports show low recov-
eries (13% to 40%) of VTEC from PCR -
positive samples; thus, the number of fi eld
isolates for further investigation can be
limited. VTEC serotypes possessing the eae
gene and toxin subtypes commonly associ-
ated with human disease isolates have been
detected in raw milk cheeses (Hussein and
Sakuma, 2005 ; Stephen et al., 2008 ), although
Pradel et al. (2008) found few VTEC strains
from dairy foods to contain the eae , espP ,
and kat P genes that are commonly associated
with disease - causing strains.
VTEC has been shown to have the poten-
tial to survive not only in high - moisture soft
or semi - soft cheeses, but also in hard - ripened
cheeses. Although viable VTEC decrease
with ripening time (Schlesser, 2004 ;
Luukkonen et al., 2005 ) in hard cheeses, the
pathogen could still be detected after 158
days of ripening of a cheddar cheese. A studyinternational outbreak during 1983, ETEC
027 : H20 (a shiga - toxin - producing strain)
was isolated from patients and the incrimi-
nated cheese. A recurrent contamination
problem at the French Brie cheese factory
was inferred due to the isolation of the organ-
ism in batches produced six weeks apart.
Studies have demonstrated the increase in
ETEC populations during the fi rst four to six
hours of cheddar and Colby - like cheese man-
ufacture, with a slow gradual decrease over
a 6 - to 12 - week period of ripening, depend-
ing on ripening temperature (Ryser, 2001 ).
Esherichia coli serotype 0157 : H7 is the
predominant foodborne pathogen among the
VTEC. Although non - dairy products such as
ground beef have been associated with the
more serious outbreaks, cheeses have been
responsible for outbreaks leading to the
development of HUS or even death. In 1998,
one of the larger outbreaks, involving 55
laboratory confi rmed cases of E. coli
0157 : H7 infection, occurred in Wisconsin.
This was linked to consumption of fresh
cheese curds that had inadvertently been pro-
duced using vats previously used to produce
cheese made from unpasteurized (raw) milk.
In Alberta, Canada, unpasteurized Gouda
cheese was responsible for an outbreak of 13
E. coli 0157 : H7 infections in 2002. The
organism was recovered from two samples (n
= 26) of the implicated cheese; one sample
was positive for E. coli 0157 : H7 104 days
post production. A number of outbreak cases
had consumed small free samples of the
cheese at a local market, indicating signifi -
cant contamination of the product and/or a
highly pathogenic organism. The source of
the E. coli contamination was not traced
during the follow - up investigation.
During the 1990s, a number of outbreaks
were reported in the UK that were linked to
cheese made from unpasteurized milk (Table
3.3 ). Although hygiene and sanitation prac-
tices at the production plants were satis-
factory, there were a number of confounding
factors which may have contributed to E. coli
0157 : H7 in the fi nal product implicated in